Engine power section for piston engines, particularly V-engines

ABSTRACT

An engine power section for piston engines, particularly V-engines, having a power unit block made of an iron material arranged in a casing of light metal. In order to achieve a stiff weight-reducing power unit block, a flange plate used for limiting the crank space as well as for the connection with the casing is arranged offset relative to a cylinder from its lower end toward its upper end with its front side surface center of gravity at a distance on this side of the bearing center plane of a crankshaft bearing, which corresponds at least to a largest possible distance of the surface center of gravity of a reinforcing profile of a bearing frame on the other side of the bearing center plane. The crankshaft bearings are connected with the flange plate by way of struts.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to an engine power section for piston engines,particularly V-engines.

For reducing the weight of an engine power section, it is basicallyknown to manufacture the power unit block, which is highly loaded and isessentially formed of the cylinders with directly or indirectlyshaped-on crankshaft bearings, preferably of an iron material, and toconstruct the less loaded power section walls separately of a lightermaterial or one which is manufactured with a particularly thin wall.

One example of this construction principle for the engine power sectionof a liquid-cooled internal-combustion engine is known from BritishPatent Document GB-PS 678 903, in which case the power section wallsadjoining the crank space as well as the power section walls used forcovering the cylinder coolant spaces are made of metal sheets. Incontrast, for achieving the required stability, the power unit block hasa relatively massive construction with end-side front walls between thecover plates and base plates of the cylinders, heavy bearing blocksbeing arranged in one piece on the base plate.

Disadvantages of this known engine power section and of the engine powersection known from British Patent Document GB-PS 695 972 are in eachcase a moderate weight reduction as well as corrosion and sealingproblems, particularly in the connection points of the structuralcomponents made of different materials. In addition, there are problemsconcerning acoustics.

For reducing particularly the acoustic problems, an engine power sectionfor a liquid-cooled internal-combustion engine is known from U.S. Pat.No. 4,446,827 which comprises a power unit block which has a massivedesign corresponding to the above-mentioned British Patent DocumentGB-PS 678 903, to which separate power section walls are assigned whichare made of a very sound-absorbing material, such as rubber, plastic orresin.

According to German Registered Utility Patent DE-U 94 12 637, corrosionand sealing problems for an engine power section of a liquid-cooledinternal-combustion engine designed of different materials is avoided inthat a light-metal power section is poured around a power unit blockmade of gray cast iron, the coolant spaces being constructed exclusivelyin the light metal power section. A disadvantage in this case is themassive design of the power unit block with engine baseboards arrangedon the crankshaft bearing blocks by way of web-type supports, whichbaseboards are connected with the light metal power section in amaterial-locking manner in the oil pan connection area of the lightmetal power section. This heavy design results in another disadvantagein that these engine baseboards connected in a material-locking mannerwith the bearing blocks act as structure-borne noise bridges andacoustically excite at least the crank space covers of the light metalpower section which are connected with them in a material-lockingmanner.

Further, from European Patent Document EP-A 0 554 575, which waspublished before German Patent Document DE-U 94 12 637, an engine powersection for a liquid-cooled internal-combustion engine is known in thecase of which a power unit block also made of gray cast iron is castinto a light metal power section. For reducing the weight of the powerunit block, cylinders arranged in a row are arranged in amaterial-locking adjacent manner and carry massively designed bearingblocks arranged by way of spaced flat webs in the connection areas.During the casting into the light metal power section, the flat webs andthe bearing blocks are integrated in a material-locking manner intransverse walls connected with the light metal power section. Thissupport of the crankshaft bearings with respect to a crank space powersection wall which is designed for reasons of stability and requireshigh expenditures of material acts as a structure-born sound bridgewhich acoustically excites the light metal power section.

Finally from Japanese Published Patent Application 4-121 443, a powerunit block is known for a liquid-cooled internal-combustion engine whichhas a shaped-on cylinder head. This design, which is known as a"monoblock", comprises a base plate which is constructed at the lowerend of the cylinder bushes and on which, on the one hand, a casing isdetachably fastened which surrounds the monoblock and on which, on theother hand, massively constructed crankshaft bearing blocks are arrangedwhose bearing caps are arranged by way of longitudinal webs in a bearingframe which disadvantageously is designed to require high expendituresof material.

The characteristic which the above-indicated state of the art has incommon is the fact that resistance to bending and torsion required for apower unit block is achieved predominantly by way of cylinders which areconnected with one another, specifically either by their siamese-typeattached arrangement or their arrangement between cover and base flangeplates connected in one piece in a material-locking manner which, inaddition, are connected by way of front plates.

The above-mentioned type-forming Japanese Published Patent Application4-121 443 shows a particularly stiff power unit block which, however, isalso heavy because of the cylinder head which is provided instead of thecover flange plate and which is arranged in a one-piece material lockingmanner, which power unit block has a massive bearing frame for thebearing caps of the crankshaft bearings.

It is an object of the invention to provide a light weight power unitblock with cylinders which has a high design stability which isinsignificantly increased by the cylinders, for a light-weight enginepower section.

This object is achieved by arranging the flange plate to be offsetrelative to the cylinder from its lower end to its upper end with itsface-side surface center of gravity at a distance on this side of thebearing center plane of the crankshaft bearings, which corresponds atleast to a largest possible distance of the surface center of gravity ofa profile of the stiffening element of the bearing frame on the otherside of the bearing center plane, the crankshaft bearings beingconnected by way of struts with the flange plate.

It is the basic idea of the invention to arrange devices of the powerunit block arranged in the longitudinal direction of the engine relativeto the axis of rotation of the crankshaft at the largest possibledistance in a connection or achieving a high moment of inertia and thusa high moment of resistance, in which case the effective distancesrequired for this purpose are, on the one hand, achieved by way of thedesign of the bearing frame with at least one stiffening elementprovided particularly low below the crankshaft and, on the other hand,by a flange plate which is advantageously easily arranged to bedisplaced at a far distance in the direction of the vertical axis of thecylinder or cylinders from the axis of rotation of the crankshaft. Asthe result of the flange plate integrated according to the inventionwith the stiffening element of the bearing frame in a connection, thecylinder as the element providing significant stability is eliminated,whereby the cylinder or cylinders can advantageously be constructed tohave a thin wall.

In addition, by means of the invention, the piston stroke and thecylinder diameter can be defined without taking into account the designstability of the power unit block, with the advantage that alsolarge-volume, high-power piston engines can be constructed to berelatively low. With the free selection of the largest possibledistances of devices pointing in the longitudinal direction of theengine from the plane of the axis of rotation of the crankshaft, theinvention offers the advantage with respect to a light construction ofthe power unit block that these devices (flange plate, stiffeningelements) can have a relatively thin-walled design while the stabilityis high.

Advantageous further developments of the engine power section accordingto the invention achieve a high design stability of both structuralcomponents individually and in a functional connection by means of openand hollow profiles which are connected with one another in a one-piecematerial-locking manner for the power unit block manufactured preferablyof gray cast iron as well as for the casing made of light metal which isin one piece with the power section walls in each case at lowexpenditures of material.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described by means of a preferred embodimentillustrated in the drawing.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a power unit block for a V-engine with apartially shown casing;

FIG. 2 is a cross-sectional view of the power unit block and of thecasing according to Line 2--2 in FIG. 1.

An engine power section 1 for a liquid-cooled piston internal-combustionengine 2 designed as a V-engine comprises a power unit block 3 and acasing 4 which is separate from it and is formed in one piece from powersection walls and is made of a material which is lighter than that ofthe power unit block 3. For the connection with the casing 4, the powerunit block 3 is equipped with flange plates 5 which are in each case onone side connected with cylinders 6 and on the other side with dividedcrankshaft bearings 7, their bearing caps 8 being arranged in a bearingframe 9 with stiffening elements 10 pointing in the longitudinaldirection of the engine.

For achieving a light-construction power unit block 3 with a highresistance to bending and torsion, according to the invention, theflange plates 5 are arranged to be offset relative to the cylinders 6from their lower ends to their upper ends with their respectivefront-side surface centers of gravity at distances on this side of thebearing center plane 11 of the crankshaft bearings 7, these distancescorresponding at least to the largest possible distances of the surfacecenters of gravity of the profiles of the stiffening elements 10 of thebearing frame on the other side of the bearing center plane 11, and thecrankshaft bearings 7 being connected by way of struts 12 with theflange plates 5.

The power unit block 3 constructed according to the invention forms aspatial connection whose moments of resistance to bending and torsionare advantageously achieved without an integration of the cylinders 6essentially by way of the devices of the flange plate 5 which in eachcase have the largest possible distance from the bearing center plane 11and point in the longitudinal direction of the engine, in combinationwith the stiffening elements 10 of the bearing frame 9.

A light weight, while the stability is high, is achieved in anotherembodiment according to the invention in that the crankshaft bearings 7are in each case connected, by way of hollow struts 13 arranged on bothsides essentially in a transverse plane of the engine, in a one-piecematerial-locking manner with the flange plates, in which case eachbearing block 7', which is preferably constructed in the manner of ahalf-ring, by means of radial flanges 14, forms a U-profile which isopen on the cylinder side or flange plate side, with transitions 15reinforcing the hollow struts 13 in the connection area.

Further, for the purpose of stability at a low weight, while utilizingan installation space provided by an oil pan which is not shown, it isprovided that each bearing cap 7" and 8 has projections which arearranged on the opposite side in the longitudinal direction of theengine in a spaced manner, pointing laterally deep downward relative tothe bearing center plane 11, in which case the relatively thin-walledprojections 16 by means of coverings 17 form essentially closed hollowprofiles 18 which are connected with hollow beams 19 as reinforcingelements 10 which, for matching the projections 16, are constructed intheir cross-section to be triangular and thin-walled.

The power unit block 3 is preferably made of vermicular gray cast iron(GGV) in a one-piece, material-locking manner at least in thecircumference of the flange plates 5 with the crankshaft bearings 7arranged by way of the hollow struts 13, including the bearing frame 9.For dividing the crankshaft bearing 7, the bearing frame 9 with thebearing caps 7" is preferably separated by means of a breakingseparation from the bearing blocks 7'. For the breaking separation, theprocess suggested in the German Patent Document P 195 47 389 is used forforming breaking separating notches, particularly in combination with adevice suggested in PCT Application PCT/EP 95/00875.

The bearing frame 9, which is separated from the power unit block 3 bymeans of "cracking", can be connected with the power unit block 3 bymeans of two studs 20 provided for each crankshaft bearing 7 which canbe screwed into the hollow struts 13. The studs 20 which are preferablyarranged essentially at a V-angle of the V-engine 2 obliquely penetratethe breaking separation surfaces preferably arranged in the bearingcenter plane 11, whereby the transverse forces in each crankshaftbearing 7 are securely transmitted by way of the braced breakingseparation surface by means of the only two provided studs 20. Thesereduced screwing expenditures advantageously result in a narrow bearingframe with stiffening elements 10 or hollow beams 19 which can bearranged below the bearing center plane 11.

As illustrated in the figures, the flange plates 5, which are arrangedin a roof-type manner, are, along their outer longitudinal areas,connected in a one-piece, material-locking manner with the crankshaftbearings 7 by way of hollow struts 13 arranged in a V-shapecorresponding to the studs 20. Between the hollow struts 13, which areadvantageously arranged essentially in parallel to the axes of thecylinders 6, the flange plates 5, which are connected in one piece inthe center, are connected by way of this connection area with eachbearing block 7', in addition, by means of hollow supports 21. Thesesupports 21 are used for diverting force in the vertical axis of theV-engine 2 for avoiding a critical load on the hollow struts 13. Forreinforcing the connection area of the flange plates 5, a longitudinalduct 22 is provided which is used, for example, in an interaction withthe hollow supports 21 for supplying lubricating oil to the bearings 7.

As addressed above, by means of the invention, a power unit block 3 isachieved without the cylinders 6 as a spatial connection of a highresistance to bending and torsion. Thus, according to the requirements,either insertable cylinders 6 can be selected or cylinders 6 which arefixedly connected with the respective flange plate 5. In the lattercase, these penetrate the flange plates 5 preferably obliquely forachieving a stiffer connection between the respective cylinder 6 and theflange plate 5 against operating vibrations which, in addition, in thecase of cylinders 6 spaced in rows, are reduced by way of bridges 23arranged in the direction of the rows between the cylinders 6. Inaddition, the cylinders 6 stand free in the respective coolant withoutany pouring of additional material around them.

For a durable connection of the power unit block 3 with the one-piececasing 4, the flange plates 5 have edges 24 in the longitudinal andtransverse direction of the engine which are each cambered by means oflarge radii and which, by way of additional smaller radii, change intoone another at the corners of the engine power section. Also, the edges24 are designed, for example, as flanges 25 with a T-shapedcross-section. As an alternative to the flanges 25, the edges 24 mayalso have a fracture-type rough surface for the form-locking andforce-locking connection with the light-metal casing 4. Furthermore, theflanges 25 may also have a fracture-type rough surface.

By means of this development of the edges 24 on the flange plates 5, acasing 4 made of a light metal casting which is in one piece with outerand inner longitudinal-side as well as front-side power section wallscan be assigned to the power unit block 3, in which case, thelight-metal casing 4, which during cooling is prevented from shrinkingby the flange plates 5 of the power unit block 3, is connected by way ofthe cambered edges 24 in a uniformly form-locking and force-lockingmanner with the flanges 25 of the flange plates 5 in a liquid-tightfashion.

The casing 4 is advantageously reinforced in that the cylinders 6, whichare connected in a one-piece material-locking manner with the flangeplates 5, each end in a cooling space cover plate 27 provided with thecooling openings 26, which cover plate 27 is connected in a one-piece,material-locking manner with the casing 4.

For further reinforcing the casing 4 and thus the engine power section1, interior longitudinal-side power section walls 28 with base and coverwalls 29 and 30 crossing the V-space form a hollow support 31 whichreinforces the rows of cylinders 6 and which, as a coolant duct, isconnected with a pump housing 32 between valve gear shafts molded on inone piece (FIG. 2).

For achieving a light-construction casing 4, it is also provided thatthese connection points 34 for auxiliary assemblies and/or bearingsupports arranged between an oil pan flange 33 provided in the area ofthe bearing center plane 11 and the flange connection 25 with the flangeplates 5 are connected by way pins 35 arranged on adjacent hollow struts13 which are preferably used for the arrangement of screwed connectionpoints.

In order to keep higher loads away from the light-metal casing 4, aseparate connection flange 36 for a transmission, which is not shown, isassigned to the encased power unit block 3 on the output side, whichconnection flange 36 can be connected with the power unit block 3 in thecenter area and in the two outer areas of the flange plate 5 above theoutput-side crankshaft bearing 7 and can be connected with the bearingframe 9 in the area of the hollow beams 19 below this bearing 7 in eachcase by way of screwed connections 37.

The weight advantage which can be achieved by means of the invention isparticularly important in the case of multi-cylinder piston engines of aV-construction but may also be advantageous for single-bank engineshaving one or several cylinders.

What is claimed is:
 1. Engine power section for piston engines,comprising:a power unit block which can be connected with a separatecylinder head and which is equipped with separate power section walls ofa casing made of a different material, the power unit block comprising aflange plate which carries a cylinder and connects the power sectionwalls as well as divided crankshaft bearings, bearing caps arranged in abearing frame with at least one engine-longitudinally-directedreinforcing element, struts applied separately from the cylinder to theflange plate by which the crankshaft bearings are connected with theflange plate, the flange plate being constructed as a carrying elementfor a cylinder and arranged offset away from a lower end toward an upperend thereof such that a largest possible distance of a surface center ofgravity of the flange plate, viewed on a face side from a bearing centerplane of the crankshaft bearings, is achieved, said largest possibledistance corresponding to at least a distance of a surface center ofgravity of a profile of the reinforcing element viewed on the face sidefrom the bearing center plane.
 2. Engine power section according toclaim 1 wherein each bearing is connected in a one-piecematerial-locking manner with the flange plate by way of hollow strutsarranged substantially on both sides in an engine transverse plane, andeach bearing block is designed in the manner of a half-ring with radialflanges and forms a U-profile which is open on the flange plate side,with transitions which reinforce the hollow struts at least in sections.3. Engine power section according to claim 1 wherein each bearing caphas projections which are arranged in a mutually spaced manner relativeto the bearing center plane and point laterally downward, and theprojections having coverings to form substantially closed hollowprofiles which are connected with hollow beams as reinforcing elementswhich have a substantially triangular cross-section and a thin-walledconstruction.
 4. Engine power section according to claim 1 wherein theflange plate with the crankshaft bearings arranged by way of the hollowstruts, including the bearing frame, are constructed in one piece ofgray cast iron, and the bearing frame with the bearing caps is separatedfrom the bearing blocks by a breaking separation, and can be connectedwith the power unit block via two studs which are provided for eachcrankshaft bearing and can be screwed into the hollow struts.
 5. Enginepower section according to claim 1 wherein, in the case of a V-engine,flange plates, which are arranged in the manner of a roof, are connectedin one piece in the center, and are connected by way of this connectionarea via hollow supports with each bearing block, and wherein eachcrankshaft bearing is connected in a one-piece material-locking mannerby way of two hollow struts arranged in a V-shape in an enginetransverse plane with outer longitudinal areas close to the flange ofthe flange plates.
 6. Engine power section according to claim 5, whereinthe flange plates are connected in the center by way of a longitudinalduct, which interacting with the hollow supports, is used for supplyinglubricating oil to the crankshaft bearings.
 7. Engine power sectionaccording to claim 5, wherein the flange plates, which are arranged inthe manner of a roof, are each obliquely penetrated by the respectivecylinders of each bank and are connected with these in a one-piecematerial-locking manner, and wherein the cylinders which are mutuallyspaced in a row are connected with one another by way of bridgesarranged in the direction of the row.
 8. Engine power section accordingto claim 5, wherein the connected flange plates have edges which areeach cambered by means of large radii in the longitudinal and transversedirection of the engine, which edges are connected to the engine powersection corners by way of additional radii, the edges being designed asflanges with a T-shaped cross-section.
 9. Engine power section accordingto claim 8, wherein the connection surfaces of at least one of the edgesand of the flanges of the flange plates with the light-metal casing havea fracture-type rough surface.
 10. Engine power section according toclaim 5, wherein the casing is in one piece with outer and innerlongitudinal-side and front-side power section walls and is made oflight metal is in a form-locking and force-locking liquid-tightconnection with the flanges of the flange plates by a casting process,and wherein the cylinders arranged in the flange plates each end in acooling space cover plate which may be provided with coolant openingsand is in a one-piece material-locking manner connected with the lightmetal casing.
 11. Engine power section according to claim 5, wherein theinner longitudinal-side power section walls with the base and coverwalls crossing the V-space form a hollow support which reinforces thebanks of the cylinders and which, as a coolant duct, is connected with apump housing arranged on the front side between valve gear shafts moldedon in one piece.
 12. Engine power section according to claim 5, wherein,on the casing, connection points for at least one of auxiliaryassemblies and bearing supports provided between an oil pan flangeprovided in the area of the bearing center plane and the flangeconnection with the flange plates are connected by way of pins arrangedon adjacent hollow struts.
 13. Engine power section according to claim5, wherein a separate connection flange is assigned to the encased powerunit block on an output side and can be connected in the center area andin both outer areas of the flange plates above an output-side crankshaftbearing and with the bearing frame in the area of the hollow beams belowthe output-side crankshaft bearing in each case by way of screwedconnections with the power unit block.
 14. Engine power sectionaccording to claim 5, wherein the cylinders, arranged on theircircumferences in each case without being surrounded by pouredadditional material, are acted upon by a coolant of the pistoninternal-combustion engine.